Posi trac

[Babby]

I have a 71 numbers matching ss. It came with a peg leg rear end but am wanting to add a posi trac. I like the idea of having an all original car (this car seems to have everything that it came from the factory with). Just wondering if adding an aftermarket unit would have a negative effect on that? Also any suggestions on which posi unit seems to be the best. 

[Canuck]

I don’t think that upgrade would devalue the car. I suggest you keep the original parts though. My 71 SS was changed to a posi as well.

[cny first gen 71]

I agree Aaron,  Tom always suggested detroit locker posi units. Probably want to change gears too, but don't go with too much gear so it's still usable without over drive.

[Canuck]

3 hours ago, cny first gen 71 said:

I agree Aaron,  Tom always suggested detroit locker posi units. Probably want to change gears too, but don't go with too much gear so it's still usable without over drive.

I had 3.73 in mine when I got it. Changed to a 3.07 and much happier with the way I use the car. I drive a lot of highway.

[TheBMan]

58 minutes ago, Canuck said:

I had 3.73 in mine when I got it. Changed to a 3.07 and much happier with the way I use the car. I drive a lot of highway.

I agree, Aaron. 3.73 is not a friendly gear with a Turbo 350 or Turbo 400. Snappy around town, insufferable on the highway.

[Scott S.]

Welcome to the club Scott...

Just wondering, I'm assuming that being a numbers matching SS, you're dealing with a 12 bolt differential ?

If so, and you're wanting to keep her as "factory" as possible, (some purist are VERY picky...lol) just adding the plates and springs to make it a posi is probably the best route.

If you're changing the gear ratio, just remember that G.M. has 4 different carriers depending on which ratio you use. So you might wind up changing the entire carrier, ring and pinion. 

[DragCat]

3 hours ago, Scott S. said:

If you're changing the gear ratio, just remember that G.M. has 4 different carriers depending on which ratio you use. So you might wind up changing the entire carrier, ring and pinion. 

Posi is a plus IMHO . There are many options so do your research and pick what's best for you. My 70SS had a posi 12 bolt, the original series 2 unit. My buddy had a series 3 and 355 gears "in stock" so we upgraded. Works for me 🤣

[Dtret]

I agree with Aaron. 
my 71SS was a 3:31 peg. I kept the same gear and changed carrier. 

[Babby]

Yes it is a 12 bolt and has 3:73’s which I thought drove rather nicely, even at 120mph the other day 😉. I do agree a posi is a must on an SS. Get even back tire wear that way lol

[S.Maug]

A paired set of black marks is mandatory.   POSI FOR LIFE  !!!

[Scott S.]

Is that a set of two ????  Or four ????

D'oh..... A deer...... A female deer. (H.Simpson)